DESCRIPTION (Investigator's Abstract) The purpose of the CRYO-ROP Follow-up Visual Acuity Center is to implement the assessment of visual function in the follow-up of three groups of children who were participants in the Multicenter Cryotherapy for Retinopathy of Prematurity (CRYO-ROP) Study. The first group consists of 256 children who developed 5 contiguous or 8 total clock hours of stage 3 retinopathy of prematurity (ROP) with plus disease and were participants in the randomized portion of the trial. The second group consists of 67 children, the "special prethreshold" group, who developed fewer than 5 contiguous or 8 total clock hours of stage 3 ROP with plus disease. These groups will be followed as part of the Phase 11 CRYO-ROP Follow-up Study. The third group consists of 539 children with birth weights less than 1000g at five of the 23 study centers. These children developed no ROP or less severe ROP than children in the other two groups, and they will be followed as part of the CRYO-ROP Natural History Follow-up Study. Children in all three groups will receive assessments of monocular visual acuity, monocular contrast sensitivity, monocular color vision, and stereopsis at age 9 years, and assessments of monocular visual acuity and monocular visual field size at age 10 years. In the randomized and special prethreshold groups, assessments will be conducted by three Testers who travel to the local centers. These three Testers, plus two non-traveling testers, will conduct the assessments of the patients in natural history group. The Visual Acuity Center will train Testers in the methods used to assess functional vision, will monitor the activities of the Testers as they test randomized and special prethreshold patients in 23 centers and natural history patients in five centers, will assure that quality control is maintained, and will participate in data analysis and writing of manuscripts related to visual function in the study population.